Fluid pumps of conventional design typically have seal and mounting problems associated with them so that improvements are always being sought to minimize such problems, if possible. For instance, one type of fluid pump made by Coleco Corporation has a seal which requires a supplementary lubricant to insure seal life. Moreover, to meet requirements of Underwriters Laboratories requiring double insulation, the motor shaft has to be separated with an air gap of approximately 1/8 of an inch. This is accomplished by separating the shafts by interconnecting two spaced shaft segments with a water slinger. The problem with this design is as follows:
1. There is excessive run-out of the two motor shaft segments and the water slinger interconnecting the shaft segments. This condition causes the shaft coupled to the impeller to run in an orbital path, causing seal problems to be created due to seal oscillation, premature work hardening of seal material and seal lip skipping. PA1 2. The water slinger is costly to manufacture due to Underwriter Laboratory requirements and close tolerances on dimensions. PA1 3. The seal requires a special lubricant to allow for durability without burnout. PA1 4. The shaft segment coupled to the impeller requires high quality surface finish and surface preparation to allow the seal to function properly. PA1 5. In addition to the foregoing, the cost of the components is relatively high.
In another prior art fluid pump, such as one of the type made by Doughboy Corporation, the motor drive shaft coupled to the impeller is of a one-piece construction and the base seal requires an outer metallic can for housing a rubber seal and forming a stop for a pressure spring. A carbon ring mates to a ceramic seal ring to seal the pump cavity.
The problems associated with this last-mentioned prior art fluid pump are that the metallic seal can is in direct contact with the pool water so that the rear motor pump mounting bracket has to be of an insulating material, such as plastic, to meet Underwriter Laboratory requirements. Moreover, the seal pressure spring is sensitive to spring rate (pressure) because of low motor starting torques. This condition requires very close assembly tolerances which are costly. Other problems include the high cost of seal assembly and the fact that the motor pump mounting base requires low tolerance manufacturing techniques.
Because of the foregoing drawbacks in prior art fluid pumps, a need exists for improvements in a fluid pump in which a motor drive shaft is coupled to an impeller through a seal for isolating a pump cavity containing the impeller. The present invention satisfies this need.